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Search Results: 1 - 10 of 448613 matches for " J. L. Walters "
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Physical activity, weight status and diet in adolescents: are children meeting the guidelines  [PDF]
Spencer E. Boyle, Georgina L. Jones, Stephen J. Walters
Health (Health) , 2010, DOI: 10.4236/health.2010.210167
Abstract: Childhood obesity is on the increase and maintaining regular physical activity and consuming a healthy diet have become essential tools to combat the condition. The United Kingdom government has recommended guidelines for optimal levels of diet and activity in children. The aim of this paper is to describe and compare self-reported physical activity levels, diet, and Body Mass Indices (BMI) amongst adolescent children, aged 11-15, in the South West (SW) and North West (NW) regions of England and to see if these children were meeting the current targets for optimal levels of: physical activity; fruit/vegetable consumption; fat consumption and BMI. We report the results of a cross-sectional survey of four secondary schools and 1,869 children using the self-reported Western Australian Child and Adolescent Physical Activity and Nutrition Survey (CAPANS) physical activity instrument and a food intake screener questionnaire, in summer and winter. We found that 25% (469/1869) 95% CI: 23% to 27%, of children engaged in 60 minutes of moderate to vigorous physical activity per day; 53% (995/1866) 95% CI: 51% to 56%, took 5 portions of fruit and vegetables per day; while 22% (407/1861) 95% CI: 20% to 24% consumed recommended amount of fats, and 23.7% (276/1164) 95% CI: 21% to 26%, of pupils were obese or overweight as classified by their BMI. Self reported physical activity in young people regardless of area is lower than previously reported and the lack of students engaging in 60 minutes moderate to vigorous activity could have serious public health consequences. If sustained, this could lead to more overweight adults, and more ill health.
A Note on the Overall Magnification of a Gravitational Point-Source-Point-Lens System
S. J. Walters,L. K. Forbes
Physics , 2015,
Abstract: The total magnification due to a point lens has been of particular interest as the theorem that gravitational lensing results in light amplification for all observers appears to contradict the conservation of photon number. This has been discussed several times, and various resolutions have been offered. In this note, we use a kinematic approach to provide a formula for the magnification factor for the primary image accurate to first order and valid for rays leaving the source at any trajectory. We thus determine the magnification over a sphere surrounding the system. A new result found is that while the magnification dips below unity far from the optical axis as noted by others, it returns to unity directly behind the source.
Dynamic Shocks in the Inhomogeneous Environment of the Cygnus Loop
N. A. Levenson,J. R. Graham,J. L. Walters
Revista mexicana de astronomía y astrofísica , 2003,
Shell Shock and Cloud Shock: Results from Spatially-Resolved X-ray Spectroscopy with Chandra in the Cygnus Loop
N. A. Levenson,J. R. Graham,J. L. Walters
Physics , 2002, DOI: 10.1086/341802
Abstract: We use the Chandra X-ray Observatory to analyze interactions of the blast wave and the inhomogeneous interstellar medium on the western limb of the Cygnus Loop supernova remnant. This field of view includes an initial interaction between the blast wave and a large cloud, as well as the encounter of the shock front and the shell that surrounds the cavity of the supernova progenitor. Uniquely, the X-rays directly trace the shock front in the dense cloud, where we measure temperature kT = 0.03 keV. We find kT~0.2 keV in regions where reflected shocks further heat previously-shocked material. Applying one-dimensional models to these interactions, we determine the original blast wave velocity v_bw~330 km/s in the ambient medium. We do not detect strong evidence for instabilities or non-equilibrium conditions on the arcsecond scales we resolve. These sensitive, high-resolution data indicate no exceptional abundance variations in this region of the Cygnus Loop.
Physical activity among adolescents and barriers to delivering physical education in Cornwall and Lancashire, UK: A qualitative study of heads of PE and heads of schools
Spencer Boyle, Georgina L Jones, Stephen J Walters
BMC Public Health , 2008, DOI: 10.1186/1471-2458-8-273
Abstract: Seventeen semi-structured qualitative interviews were carried out with a snowball sample of HOPE and HS in schools in the Northwest and Southwest of England. Thematic data analysis using NVIVO was used to identify emergent themes.17 core themes were generated, 12 of which confirmed the findings from similar research. However, five themes relating to 'ethos of performance/elitism', 'lower fitness leads to lower ability', 'undervaluing activities within PE dept' or school as a whole', 'role of the school' and 'PE department doing all it can' offer valuable new insight into the factors which may encourage or prevent PA inside or outside the curriculum.Despite many positive perceptions of the delivery of PE in schools, it is evident that barriers still exist within that delivery which discourages physical activity. More research is needed to particularly address the complex issues of elitism and the ethos of PA in schools.Recent data indicate that almost one in four young people in the UK (23.7% of 11–15 year old males and 26.2% females) are now classed as obese [1]. There is much speculation about the causes of obesity in young adolescents. However, it has been reported that one of the leading contributory factors of childhood obesity is a lack of physical activity (PA) [1]. Although a common standard of the optimum level of young people's physical activity has yet to be universally agreed upon [2], the UK government (as part of its physical education school sports club links strategy), set a target in 1999 that 85% of school children should take part in two hours per week of high quality sport and physical education (PE) and a variety of new initiatives were introduced in schools to help children achieve this target by 2008 [3].Nevertheless, despite these new initiatives there is still controversy amongst physical educators and academics over whether young people are obtaining adequate levels of PE and are sufficiently physically active. For example, according to a Sp
A kinematical approach to gravitational lensing using new formulae for refractive index and acceleration
S. J. Walters,L. K. Forbes,P. D. Jarvis
Physics , 2010, DOI: 10.1111/j.1365-2966.2010.17380.x
Abstract: This paper uses the Schwarzschild metric to derive an effective refractive index and acceleration vector that account for relativistic deflection of light rays, in an otherwise classical kinematic framework. The new refractive index and the known path equation are integrated to give accurate results for travel time and deflection angle, respectively. A new formula for coordinate acceleration is derived which describes the path of a massless test particle in the vicinity of a spherically symmetric mass density distribution. A standard ray-shooting technique is used to compare the deflection angle and time delay predicted by this new formula with the previously calculated values, and with standard first order approximations. Finally, the ray shooting method is used in theoretical examples of strong and weak lensing, reproducing known observer-plane caustic patterns for multiple masses.
Description and evaluation of the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4)
L. K. Emmons,S. Walters,P. G. Hess,J.-F. Lamarque
Geoscientific Model Development Discussions , 2009,
Abstract: The Model for Ozone and Related chemical Tracers, version 4 (MOZART-4) is an offline global chemical transport model particularly suited for studies of the troposphere. The updates of the model from its previous version MOZART-2 are described, including an expansion of the chemical mechanism to include more detailed hydrocarbon chemistry and bulk aerosols. Online calculations of a number of processes, such as dry deposition, emissions of isoprene and monoterpenes and photolysis frequencies, are now included. Results from an eight-year simulation (2000–2007) are presented and evaluated. The MOZART-4 source code and standard input files are available for download from the NCAR Community Data Portal (http://cdp.ucar.edu).
Sample size and power estimation for studies with health related quality of life outcomes: a comparison of four methods using the SF-36
Stephen J Walters
Health and Quality of Life Outcomes , 2004, DOI: 10.1186/1477-7525-2-26
Abstract: Health Related Quality of Life (HRQoL) measures are becoming more frequently used in clinical trials as primary endpoints. Investigators are now asking statisticians for advice on how to plan (e.g. estimate sample size) and analyse studies using HRQoL measures.Sample size calculations are now mandatory for many research protocols and are required to justify the size of clinical trials in papers before they will be accepted by journals [1]. Thus, when an investigator is designing a study to compare the outcomes of an intervention, an essential step is the calculation of sample sizes that will allow a reasonable chance (power) of detecting a predetermined difference (effect size) in the outcome variable, at a given level of statistical significance. Sample size is critically dependent on the purpose of the study, the outcome measure and how it is summarised, the proposed effect size and the method of calculating the test statistic [2]. For simplicity in this paper we will assume that we are interested in comparing the effectiveness (or superiority) of a new treatment compared to a standard treatment at a single point in time.HRQoL measures such as the Short Form (SF)-36, Nottingham Health Profile (NHP) and European Organisation for Research and Treatment of Cancer (EORTC) QLQ-C30 are described in Fayers and Machin [3] and are usually measured on an ordered categorical (ordinal) scale. This means that responses to individual questions are usually classified into a small number of response categories, which can be ordered, for example, poor, moderate and good. In planning and analysis, the responses are often analysed by assigning equally spaced numerical scores to the ordinal categories (e.g. 0 = 'poor', 1 = 'moderate' and 2 = 'good') and the scores across similar questions are then summed to generate a HRQoL measurement. These 'summated scores' are usually treated as if they were from a continuous distribution and were Normally distributed. We will also assume that th
Tolerance and rebound with zafirlukast in patients with persistent asthma
David W Reid, Neil L Misso, Shashi Aggarwal, Philip J Thompson, David P Johns, E Haydn Walters
Journal of Negative Results in BioMedicine , 2008, DOI: 10.1186/1477-5751-7-3
Abstract: To look for any evidence of tolerance and potential for short-term clinical worsening on LRA withdrawal. Outcome measures included changes in; airway hyperresponsiveness to inhaled methacholine (PD20FEV1), daily symptoms and peak expiratory flows (PEF), sputum and blood cell profiles, sputum CysLT and prostaglandin (PG)E2 and exhaled nitric oxide (eNO) levels.A double blind, placebo-controlled study of zafirlukast, 20 mg twice daily over 12 weeks in 21 asthmatics taking β2-agonists only (Group I), and 24 subjects treated with ICS (Group II).In Group I, zafirlukast significantly improved morning PEF and FEV1compared to placebo (p < 0.01), and reduced morning waking with asthma from baseline after two weeks (p < 0.05). Similarly in Group II, FEV1 improved compared to placebo (p < 0.05), and there were early within-treatment group improvements in morning PEF, β2-agonist use and asthma severity scores (p < 0.05). However, most improvements with zafirlukast in Group I and to a lesser extent in Group II deteriorated toward baseline values over 12 weeks. In both groups, one week following zafirlukast withdrawal there were significant deteriorations in morning and evening PEFs and FEV1 compared with placebo (p ≤ 0.05) and increased nocturnal awakenings in Group II (p < 0.05). There were no changes in PD20FEV1, sputum CysLT concentrations or exhaled nitric oxide (eNO) levels. However, blood neutrophils significantly increased in both groups following zafirlukast withdrawal compared to placebo (p = 0.007).Tolerance appears to develop to zafirlukast and there is rebound clinical deterioration on drug withdrawal, accompanied by a blood neutrophilia.The cysteinyl leukotrienes (CysLTs), LTC4, LTD4, and LTE4, contribute to airway inflammation and bronchoconstriction in asthma [1-3]. Cysteinyl leukotriene receptor antagonists (LRAs) and synthesis inhibitors are widely used as anti-asthma therapies and they have been convincingly shown in research studies to improve lung function an
Evaluation of nepafenac in prevention of macular edema following cataract surgery in patients with diabetic retinopathy
Singh R, Alpern L, Jaffe GJ, Lehmann RP, Lim J, Reiser HJ, Sall K, Walters T, Sager D
Clinical Ophthalmology , 2012, DOI: http://dx.doi.org/10.2147/OPTH.S31902
Abstract: luation of nepafenac in prevention of macular edema following cataract surgery in patients with diabetic retinopathy Original Research (1844) Total Article Views Authors: Singh R, Alpern L, Jaffe GJ, Lehmann RP, Lim J, Reiser HJ, Sall K, Walters T, Sager D Published Date August 2012 Volume 2012:6 Pages 1259 - 1269 DOI: http://dx.doi.org/10.2147/OPTH.S31902 Received: 18 March 2012 Accepted: 18 May 2012 Published: 03 August 2012 Rishi Singh,1 Louis Alpern,2 Glenn J Jaffe,3 Robert P Lehmann,4 John Lim,5 Harvey J Reiser,6 Kenneth Sall,7 Thomas Walters,8 Dana Sager9 1Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH, 2The Cataract, Glaucoma, and Refractive Surgery Center, El Paso, TX, 3Duke Eye Center, Duke Reading Center, Duke University, Durham, NC, 4Lehmann Eye Center, Nacogdoches, TX, 5Houston Eye Associates, Houston, TX, 6Eye Care Specialists, Kingston, PA, 7Sall Research Medical Center, Artesia, CA, 8Texan Eye, Austin, TX, 9Alcon Research Ltd, Fort Worth, TX, USA Background: The purpose of this study was to evaluate nepafenac ophthalmic suspension 0.1% (Nevanac ; Alcon Research Ltd) in the prevention of macular edema following cataract surgery in diabetic retinopathy patients. Methods: This was a multicenter, randomized, double-masked, vehicle-controlled study of 263 adult diabetic patients with nonproliferative diabetic retinopathy requiring cataract surgery. Patients were randomized (1:1) to instill nepafenac or vehicle three times daily beginning 1 day prior to surgery through day 90. Efficacy included the percentage of patients who developed macular edema (≥30% increase in central subfield macular thickness from baseline) and the percentage of patients with decreases of more than five letters in best-corrected visual acuity from day 7 to 90. Results: A significantly lower percentage of patients in the nepafenac group developed macular edema relative to patients in the vehicle group (3.2% versus 16.7%; P < 0.001). A significantly lower percentage of patients in the nepafenac group had best-corrected visual acuity decreases of more than five letters relative to patients in the vehicle group on day 30 (P < 0.001), day 60 (P = 0.002), and day 90 (P = 0.006). The mean central subfield macular thickness and mean percent change from baseline in macular volume were also significantly lower in the nepafenac group versus the vehicle group at days 14 through 90 (P ≤ 0.005). No safety issues or trends were identified when dosing was increased to 90 days that negatively impacted the favorable benefit/risk profile of nepafenac. Conclusion: Nepafenac demonstrated statistically significant and clinically relevant advantages compared with vehicle in preventing macular edema and maintaining visual acuity in diabetic patients following cataract surgery. These advantages were seen at multiple time points over the course of the 90-day therapy period. There was no clinically relevant increase in risk from 90 days dosing compared with 14 days. Therefo
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